Welding system for superhigh purity fluid supply pipe system

ABSTRACT

A welding system for superhigh purity gas supply system, capable of removing easily and completely the metals deposited, during the installation of the superhigh purity gas pipe system, on the outer surfaces of the portions of the pipes which are closed to the portions to be welded thereof and on the inner portions of these pipes, and capable of setting up a superhigh purity gas supply system in a short period of time. A welding system for the gas supply pipe system in which a plurality of members are connected together by welding, characterized in that a first member to be welded(113) is provided with a means for supplying an inert gas or a welding back seal gas and a means for supplying superpure water, a second member to be welded(114) being provided with a means for discharging the inert gas or back seal gas and a means for discharging the superpure water, the first and second members being welded as the inert gas or back seal gas is being supplied, the superpure water being supplied after the welding of these members has been completed, whereby the metal fume deposited on the surfaces of the welded members during the welding thereof can be washed out.

TECHNICAL FIELD

The present invention relates to a welding system for super high purityfluid supply pipe systems, and in particular, relates to a weldingsystem for super high purity gas supply pipe systems which is capable ofreducing the installation costs of supply systems and the like for superhigh purity gasses, pure water, chemicals, or the like, which arerequired for manufacturing apparatuses for high performancesemiconductor devices and the like, and which is capable of a rapid highperformance setup after installation.

BACKGROUND OF THE INVENTION

Tungsten-inert gas welding, arc gas welding, beam welding, and the like,are widely employed as methods of connecting pipes and fluid parts, suchas valves, regulators, and the like, which are employed in fluid supplypipe systems. However, in this conventional welding technology, thesurface roughness of the welded portions, and the deposition of metal onthe inner surfaces of supply system pipes as a result of metal fumesreleased from the fused portion, have not been considered. Inparticular, in conventional gas supply pipes or parts having weldedportions, no treatment was made with respect to the deposition of metalfumes generated by welding on the inner surfaces of supply system pipes,so that on contact with extremely active special material gasses, thesedeposited metals tended to corrode and be separated. As a result, theuse points, such as semiconductor manufacturing devices and the like,which employed gasses were subject to metal contamination, and this hasbeen recognized as an important factor blocking an increase inperformance of such semiconductor devices. Furthermore, while noproblems occurred over short periods of time with respect to inertcommon gasses, it has been discovered by the present inventors thatthere are some problems with reliability over longer periods.

The deposition of metal fumes as a result of the welding of fluid andgas supply pipe systems, and the surface roughness of the weldedportions, will be explained in greater detail using FIG. 4. FIG. 4 showswelded portions in which pipe materials are welded by means oftungsten-inert gas welding. In the figure, reference 401 indicates atungsten electrode, while reference 402 indicates pipe materials whichare subjected to welding. Reference 403 indicates a welded portion,while reference 404 indicates metal fumes which are released from thefused portion. These metal fumes 404 are carried by the arc gas or backseal gas flow and are deposited on the surface of the pipe material 402at the downstream side of welded portion 403, and become depositedmetals 405. These deposited metals 405 do not present the problem ofseparation with respect to inert gasses; however, when a corrosive gas,for example, hydrogen chloride gas, is caused to flow, the depositedmetals 405, which are not bonded to the surface of the material, but aremerely deposited thereon, are subject to separation. The separatingmetals comprise Fe, Ni, Cr, and Mn, which are chiefly contained in themetal materials, and because these metals exert a great influence on theLSI characteristics, the removal of these metals is a crucial problem insemiconductor production.

However, in installation methods for fluid supply pipe systems, such ascurrent semiconductor production apparatuses or the like, there has beenno effective removal of the above metal contaminants, and there hasbeen, in particular, a great desire for a welding system which can beapplied to apparatuses requiring a highly clean atmosphere.

The present invention was created in light of the above circumstances;it has as an object thereof to provide a welding system for super highpurity fluid supply pipe systems which is capable of easily andcompletely removing metals deposited at the vicinity of the surface ofthe welded portion and at the inner portions of the fluid supply system,during the installation of a super high purity fluid supply pipe system,and which is furthermore capable of setting up a super high puritysupply system in a short period of time.

Disclosure of the Invention

The present invention resides in a welding system for fluid supply pipesystems in which a plurality of members to be welded are connected bywelding, wherein a first member to be welded is provided with amechanism for supplying an inert gas or for supplying a back seal gasfor use in welding, and with a super pure water supply mechanism, asecond member to be welded is provided with a discharge mechanism forthe inert gas or the back seal gas, and with a super pure waterdischarge mechanism, and the first and second members to be welded arewelded as the inert gas or back seal gas is being supplied, and afterwelding, the super pure water is supplied, and it is thus possible towash out the metal fumes which are deposited on the inner surface of themembers to be welded as a result of welding.

Function

An inert gas or a back seal gas is supplied to the welded portion via aninert gas supply mechanism or a back seal gas supply mechanism, andthereby, it becomes possible to prevent the burning of the surface ofthe welded portion, which is the source of particle contamination.During welding, metal fumes are released from the fused portion and areredeposited at the downstream side of the welded portion.

Next, super pure water is introduced from the super pure water supplymechanism, and is passed through the welded portion and is discharged bythe discharge mechanism, and thereby, it is possible to wash out themetal which is deposited on the inner surfaces of the pipe system as aresult of welding. In order to greatly reduce the substances remainingafter the deposited metals are washed out, and to prevent secondarycontamination, super pure water is used, and in particular, water havinga resistivity of 18 MΩ·cm or more, and an amount of metals contained of100 ppt or less, is preferable. Furthermore, the water temperatureshould be within a range of 20° C.-100° C. in order to increase thewashing effect, and a range of 40° C.-80° C. is further preferable. Thewashing period differs depending on water temperature; however, in thecase of water at a temperature of 40° C., a period of approximately 1hour is required.

After washing, it is preferable that an inert gas such as nitrogen gas,Ar gas, or the like, be supplied, the inner surfaces be desiccated, anda constant clean atmosphere be maintained.

The welding system in accordance with the present invention is capableof conducting the welding, washing with super pure water, anddesiccation, by block, particularly during the installation of piping,and is capable of conducting washing and desiccation from blocks whichhave been welded, so that it is possible to install a super high purityfluid supply pipe system without sacrificing the installation speed ofthe super high fluid supply system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram showing a first embodiment of the presentinvention. FIG. 2 is a conceptual diagram showing a second embodiment ofthe present invention. FIG. 3 is a conceptual diagram showing a thirdembodiment of the present invention. FIG. 4 is a conceptual diagramshowing problems in the conventional welding technology.

Reference 101 indicates a double three-way valve, reference 102indicates a gas supply pipe, reference 103 indicates a super pure watersupply pipe, reference 104 indicates a super pure water circulationpipe, reference 105 indicates a source water tank, reference 106indicates a discharge recycling line, reference 107 indicates a particlemeasurement apparatus and a resistivity measurement apparatus,references 108 and 116 indicate double three-way valves, reference 109indicates a pipe, reference 110 indicates a discharge pipe, reference111 indicates an activated carbon column, reference 112 indicates an ionexchanging resin column, references 113 and 114 indicate pipes to bewelded, reference 115 indicates a tungsten electrode, reference 117indicates a semiconductor gas supply apparatus, reference 118 indicatesa semiconductor processing apparatus, references 201 and 206 indicateblocks of a gas supply system, references 203 and 203' indicate flowdiversion valves, reference 204 indicates a double three-way valve,reference 205 indicates a super pure water supply line, reference 301indicates a pipe, reference 302 indicates a flow diversion valve,references 303 and 304 indicate triple four-way valves, reference 305indicates a pipe, reference 306 indicates a block during super purewater washing, reference 307 indicates a super pure water supply line,reference 308 indicates a discharge line, reference 310 indicates abypass pipe, reference 401 indicates a tungsten electrode, reference 402indicates pipe materials which are subjected to welding, reference 403indicates a welded portion, reference 404 indicates metal fumes, andreference 405 indicates deposited metal.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the welding system for super high purity fluid supply pipesystems in accordance with the present invention will be explained usingembodiments; however, it is of course the case that the presentinvention is in no way limited to the embodiments described.

Embodiment 1

A first embodiment of the present invention is depicted in FIG. 1. FIG.1 shows a structural example for installing the welding system of thepresent invention in a gas supply system which supplies gas from asemiconductor fluid supply apparatus 117 to a use point, for example, asemiconductor processing apparatus 118.

By means of the opening and closing of double three-way valve 101, Argas is supplied to SUS316L pipes 113 and 114 from a gas supply systemwhich is connected to pipe 102, and this gas is discharged outside thesystem via double three-way valve 116. In this state, pipes 113 and 114are welded by means of tungsten-inert gas welding. Reference 115indicates a tungsten electrode which is employed in the welding.

Next, double three-way valves 101 and 116 are switched, super pure wateris supplied to the pipes which have been welded, the impurities such asmetal fumes and the like deposited within the pipes are washed out, andthis water is discharged to discharge line 106.

After supplying super pure water having a temperature of 30° C. for aperiod of 5 hours, three-way valves 101 and 116 are again switched,nitrogen gas is introduced into pipes 113 and 114, and the gas isdischarged, and the flow is continued until the moisture is completelypurged.

In order to evaluate the degree of cleanliness of the gas supply systemdescribed above, the following tests were conducted with respect to thegas supply system of the present invention and with respect to a gassupply system having the same form which was installed by theconventional method.

Hydrogen chloride gas having a moisture content of 1.4 ppm wasintroduced into the gas supply system from semiconductor gas supplyapparatus 117, and was maintained in the system at a pressure of 2.5Kg/cm² for a period of 12 hours. After this, 250 cc/min of Ar gas wassupplied, metal atoms present in the gas were collected on a siliconwafer at the gas introduction port of the semiconductor processingapparatus 118, and a determination of these metal atoms was conducted bymeans of TR-XSF (total reflection X-ray fluorescence spectroscopy). Inthe case of the gas supply system of the conventional example, metalssuch as Fe, Cr, Ni, Mn and the like were detected; however, no metalswere detected from the gas supply system of the present embodiment.

In the super pure water supply system shown in FIG. 1, when super purewater is not being used, the super pure water is returned to the sourcewater tank 105, and thereby, it is possible to prevent the contaminationof the water quality and of the pure water supply system. Water qualitydetection apparatuses 107, such as a particle measurement apparatus anda resistivity measurement apparatus and the like, are provided on thedischarge recycling line 106 of the super pure water which has been usedfor washing, so that the quality of the discharged water is monitored,and by means of the opening and closing of the double three-way valve108, discharged water having a relatively high degree of purity isreturned to the source water tank 105 via pipe 109, while dischargedwater having a comparatively low degree of purity is discharged outsidethe system via pipe 110. In particular, by making double three-way valve101 an automatic valve, it is possible to conduct the automatic washingand desiccation of the welded portions by setting a washing period.Furthermore, in the above example, the discharge recycling line 106 ofthe super pure water which has been employed in washing is connected tothe source water tank 105; however, it may be connected betweenactivated carbon column 111 and ion exchanging resin column 112 as well.Furthermore, an ultraviolet irradiation apparatus may be employedbetween activated carbon column 111 and ion exchanging resin column 112for the purposes of sterilization and removal of organic materialspresent in the water.

Embodiment 2

A second embodiment of the present invention is shown in FIG. 2.

FIG. 2 shows a welding system in which a fluid supply pipe system isdivided into blocks, the nitrogen purge after welding and super purewater washing is conducted simultaneously with the super pure waterwashing, and the installation speed of the fluid supply system is thusincreased.

The block 201 of the fluid supply system is at the stage at whichwelding and super pure water have been completed, and a nitrogen gaspurge is being conducted. Nitrogen gas is introduced from a super highpurity fluid supply source from one end of fluid supply block 201, andthe purging and desiccation of pipe supply system 201, which has beenwashed with super pure water, is conducted. Flow diversion valves 203are employed as gas discharge valves during welding and as waterdischarge valves during super pure water washing; in the diagram, theopen state thereof is shown, and the purged gas is discharged outsidethe system via these valves. The double three-way valve 204 is shown ina closed state. Furthermore, it is possible that only the flow diversionvalve 203 at the extreme downstream side is opened, while the remainderof the flow diversion valves 203 are closed.

Block 206 is isolated from block 201 by means of valves, and is shown atthe stage in which super pure water washing is being conducted. Thisblock 206 is connected to a pure water supply system via a doublethree-way valve 204, and the super pure water is supplied to pipe 207and conducts washing. The discharged super pure water which has beenused for washing is recycled via flow diversion valves 203'.

As described above, it is possible to conduct welding, super pure waterwashing, and desiccation, by block of the fluid supply pipe system, andthereby, it is possible to increase the installation speed.

Embodiment 3

A third embodiment of the present invention is shown in FIG. 3.

In FIG. 3, a welding system is shown which is capable of connecting asubsequent welding installation while washing a pipe system, the weldinginstallation of which has been completed. Pipe 301 is connected to aninert gas supply source or a back seal gas supply source, and this gascan be used for purging via flow diversion valves 302. The inert gas orback seal gas which is introduced into pipe 301 is supplied to a pipe305, which is in the process of installation, via triple four-way valves303 and 304 and bypass pipe 310. Furthermore, super pure water issupplied from a pipe 307, which is connected to a super pure watersupply system, to a gas supply system 306, the welding installation ofwhich has been completed, via triple four-way valve 303, and thereby,the gas supply system 306, the welding system of which has beencompleted, is washed. At this time, the discharged super pure waterwhich has been used in washing passes through discharged water line 308via triple four-way valve 304, and is either returned to the sourcewater tank shown in FIG. 1 or is discharged outside the system.

The welding system of the present embodiment is capable of increasingthe washing effect by disposing triple four-way valves 303 and 304 inthe fluid supply system at appropriate distances and conducting washingby portions, in the case in which super pure water treatment cannot beconducted uniformly with respect to inner surfaces of pipes, the weldinginstallation of which has been completed, particularly in fluid supplysystems which extend over long distances. Furthermore, in the presentembodiment, an explanation was given with respect to the time of thewelding installation; however, it is possible to dispose triple four-wayvalves in the fluid supply system at appropriate intervals, and to addsuper pure water washing in portions after the installation of theentire super high purity fluid supply system has been completed.

As explained above, in accordance with the welding system in accordancewith the present invention, it is possible to remove deposited metal inthe vicinity of the surface of the welded portions resulting from metalfumes released from the fused portion, and furthermore, desiccation isconducted by means of an inert gas with a super high degree of purityafter washing, so that even if an active special material gas, and inparticular, hydrogen chloride gas, which is corrosive, is supplied, itis possible to prevent problems such as the corrosion of the weldedportions and the separation of the deposited metal. Accordingly, byusing the welding system for super high purity fluid supply pipe systemsof the present invention, it is possible to provide a high purity gassupply pipe system having high reliability over long periods of time.

What is claimed is:
 1. A welding system for super high purity fluidsupply pipe systems in which a plurality of pipe members are to beconnected by welding and in which metal deposits caused by such weldingare to be removed, said welding system comprising:means for supplying aninert gas to a first said pipe member during a welding operation; meansfor discharging said inert gas from a second said pipe member during awelding operation; means for supplying super pure water to said firstpipe member after completion of said welding operation; and means fordischarging super pure water from said second pipe member.
 2. Thewelding system of claim 1, wherein said means for supplying an inertgas, said means for supplying super pure water, said means fordischarging an inert gas, and said means for discharging super purewater comprise valves for switching between a flow of super pure waterand a flow of inert gas.
 3. The welding system of claim 2, wherein saidinert gas comprises one of Ar gas and nitrogen gas.
 4. The weldingsystem of claim 2, wherein said inert gas comprises Ar gas to whichhydrogen gas has been added.
 5. The welding system of claim 1, whereinsaid inert gas comprises one of Ar gas and nitrogen gas.
 6. The weldingsystem of claim 1, wherein said inert gas comprises Ar gas to whichhydrogen gas has been added.
 7. The welding system of claim 1 includingmeans for, after said water supplying step, supplying an inert gas tosaid first pipe member and discharging said inert gas from said secondpipe member.
 8. A method of connecting a plurality of pipe members bywelding into a superhigh purity fluid supply system and for removingmetal deposits caused by such welding, said method comprising:weldingfirst and second pipe members while supplying an inert gas to said firstpipe member and discharging said inert gas from said second pipe member;after said welding operation supplying super pure water to said firstpipe member and discharging said water from said second pipe member. 9.The method according to claim 8 and further including the step of, aftersaid water supplying step, supplying an inert gas to said first pipemember and discharging said inert gas from said second pipe member.